Question

does smoking increase or decrease levels of hemoglobin?

Explanation:

Smoking can lead to an increase in hemoglobin levels. This is because smoking causes carbon monoxide (CO) to bind to hemoglobin in red blood cells. The body then perceives a "hypoxia - like" state (as CO - bound hemoglobin can't carry oxygen effectively), and in response, the bone marrow produces more red blood cells (and thus more hemoglobin) in an attempt to compensate for the perceived lack of oxygen - carrying capacity. Also, smoking - related lung diseases can cause chronic hypoxia, which stimulates the production of erythropoietin, a hormone that promotes red blood cell production and subsequently increases hemoglobin levels.

Answer:

Smoking generally increases levels of hemoglobin.